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Search: id:A120883
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| A120883 |
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(1/4)*number of lattice points with odd indices in a square lattice inside a circle around the origin with radius 2*n. |
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+0
1
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| 1, 3, 8, 13, 20, 28, 39, 52, 64, 79, 96, 112, 135, 154, 179, 203, 228, 255, 281, 316, 349, 382, 416, 451, 494, 532, 573, 618, 661, 707, 756, 807, 859, 910, 963, 1015, 1076, 1137, 1198, 1256, 1321, 1386, 1452, 1523, 1594, 1667, 1737, 1808, 1889, 1965, 2046, 2123
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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lim n-> infinity a(n)/n^2 = Pi/4.
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EXAMPLE
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a(3)=8 because the 8 lattice points in the first quadrant (x,y)={(1,1), (1,3), (3,1), (1,5), (5,1), (3,3), (3,5), (5,3)} all fulfil x^2+y^2 < (2*3)^2.
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CROSSREFS
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Cf. A001182.
Sequence in context: A105502 A105702 A081989 this_sequence A094110 A084535 A051838
Adjacent sequences: A120880 A120881 A120882 this_sequence A120884 A120885 A120886
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KEYWORD
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nonn
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AUTHOR
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Hugo Pfoertner (hugo(AT)pfoertner.org), Jul 12 2006
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